Fig. 3. Effects of foxa MASO on development. (A-L) Strongylocentrotus purpuratus embryos; (M-P) Lytechinus variegatus embryos. (A-C,J-L) Early-mid gastrula, (D-F) late gastrula, (G-I,M-P) pluteus stage larvae, respectively corresponding to 35 hours, 48 hours and 70 hours of development for S. purpuratus. (C,F,I,J,M,O) Control embryos treated as specified in each panel. (A,B,D,E,G,H,K,L,N,P) foxa MASO-treated embryos. The concentration of MASO injected is indicated in each panel. Black arrows (B) indicate that the SMCs reach their correct position even if a severe reduction of gut extension has occurred. (J) Fluorescent image of embryos injected with the 5'foxa-GFP fusion mRNA: all of the cells express GFP as shown by the (false) green color. (K,L) When foxa MASO is co-injected with 5'foxa-GFP mRNA embryos do not show any GFP fluorescence (K) but do display the foxa MASO phenotype (L). Fluorescent and bright field images of the same embryo. Red arrowheads (E,F,H,I) point to the foregut or to the location where the foregut should be. The increase in pigment cells occurring on MASO treatment can be seen by comparing control embryos (M,O) to MASO-treated embryos (N,P), where the pigment cells appear as dark red cells positioned throughout the aboral ectoderm on the anal side (M,N) and over the oral hood (O,P). The control embryo in O has a mouth, whereas the embryo in P injected with foxa MASO does not.